I was thinking today of bands that used classical instruments in their albums and still pulled a solid extreme metal track excluding Folk and Pagan Metal bands!!! (Of course I am not talking about Keyboards here as well but Saxophone, Cello, Violins and the likes)

I can name only a few from the top of my mind and am eager to hear more if you guys can think of anything...

At the gates,Shining,Ihsahn,Angantyr.

Please share your thoughts as I would like to explore more extreme metal (Black, Death, Thrash or the subgenres) bands that managed it correctly;

They use a contrabass as a bass guitar and it's pretty awesome because it's just used in the metallic context - instead of a lot of bs ways that supposedly "classically" influenced metal bands use. So, it makes the sound really cavernous and deep. You'll prolly dig - but it's extremely minimalist black metal.

Arcturus - Ad Astra has a string quartet on it. 'For to end and Yet Again' has some brass on them.

Maybe you're looking for stuff like Therion and Haggard?

Solefald's Icelandic Odysset pt I and II feature sax if counts.

I am looking for Extreme Metal bands that used exotic instruments and still pulled a dark and obscure metal sound (not the likes of Therion and Haggard - These bands played Distorted Classical Music with Growl and what's not).

Sigh was the first band that came to mind, especially if saxophone is a classical instrumental. I've only heard In Somniphobia in its entirety but the title track from Hangman's Hymn also had some pretty awesome use of orchestration.

Fleshgod Apocalypse use VSL that is rather poorly programmed and compressed quite a bit so it can go over the death metal. Poor man's classical really.

Sear Bliss is pretty interesting in their use of instrumentation imo. I would absolutely love to hear Emperor backed by an actual orchestra although it would probably never worked. There's often such a big difference in orchestration and treatment of the orchestra within metal that would make the real thing pale in comparison. Quite possibly because classical music is generally full of dynamics while metal has a rather limited range (most of the time at least).

Fleshgod Apocalypse use VSL that is rather poorly programmed and compressed quite a bit so it can go over the death metal. Poor man's classical really.

...There's often such a big difference in orchestration and treatment of the orchestra within metal that would make the real thing pale in comparison...

Agreed wholeheartedly. Synthesized instruments don't capture the nuance of a real musician and their instrument. Not only that, but I always feel the person writing for the instrument should be someone that has an intimate relationship with it.

The problem isn't that it's a "synthesized" (they're not synthesized instruments, they're actual sample libraries, big difference), it's that most people using these sample libraries have a) absolutely no experience in proper orchestration or classical composition b) have very little knowledge of each instrument and how it is properly played (i.e. making it sound realistic from an articulation point of view) c) they don't take the time to learn the library in and out/ have poor MIDI skills.

A lot of the music you hear on TV, in movies and in games is played with such sample libraries today and it does fool most people.

Ne Obliviscaris have a violinist. Their songs generally have ambient sections in them driven by the violin and clean guitar, and they're quite lovely to listen to.

To each their own, I guess. That was the first example that came to mind, I don't think it's badly performed and it uses lots of the standard techniques classical guitar players incorporate into their playing. Ne Obliviscaris may be a better example though. Can't really think of any others right now.